FIG. 1 conceptually illustrates a known approach of generating a navigation map with traffic information. This figure illustrates that one approach for displaying traffic data on a map is by overlaying traffic information over pre-rendered static raster images that represent different portions of the map. To illustrate this approach, this figure illustrates a generated map section 110, a traffic data object 120, and a static road tile 130.
The static road image 130 is a pre-rendered raster image of the section 110 of a map. It is a two-dimensional graphic representation of a geographical area. The road image 130 may show roads, landmarks, natural features of the geographical area (such as hills, mountains, bodies of water, vegetation, coastline), and man-made structures (such as buildings, bridges, etc.). The road image 130 may also include labels on it (such as names of streets, locations, etc.) to help specify a location.
The traffic data object 120 includes static and dynamic traffic data for the roads that are part of the static road tile 130. This information may include road conditions such as traffic congestion, detours, and traffic accidents. It also includes information that describes the layout of the roads in the static road tile 130.
The dynamic traffic data 120 is applied to the static road image 130 to generate the map section 110 that shows the traffic information along the roads that are part of the map section. The map section 110 is a portion of the map that is generated with other sections for display.
The traditional approach of overlaying the traffic data over the static road image 130 to display traffic data on a section of a map has several disadvantages. One disadvantage is that the traffic data does not always perfectly match the road layout at all zoom levels for showing the mapping at different levels of details. Another disadvantage is that the representation of traffic data often occludes the detail (e.g., names and structure of roads) that is part of the static road image. Yet another disadvantage of this approach is that the traffic data 120 is tightly coupled to the static road image 130. Every time a client device upgrades to a new version of the static road image, the traffic server has to upgrade the traffic data 120 accordingly. Furthermore, since some client devices may not upgrade to the latest version of the static road image or may not upgrade at all, the traffic server has to support multiple versions of static road images.